1. Field of the Invention
The present invention relates to a signal transmission device and a related motherboard, and more specifically, to a signal transmission device with single output configuration and a related motherboard.
2. Description of the Prior Art
With rapid development of electronic technology, a computer has powerful and various functions, such as data storage, video display, optical disk recording, and so on. Thus, the related component configuration on a motherboard becomes more complicated and more flexible, meaning that a user may have various choices in component assembly of the computer. For example, in connection of a computer screen to a computer host, a common assembly method utilizes insertion of a signal plug of the computer screen into a signal socket of a graphics processing card installed on a motherboard for driving the computer screen to display images based on signals transmitted from the computer host. But if the motherboard simultaneously has a digital visual interface (DVI) connecting port and a graphics processing card slot (e.g. a PCI-E bus), a user may have two assembly choices. One assembly choice, as mentioned above, is to utilize connection of the signal socket on the graphics processing card installed in the graphics processing card slot to the signal plug of the computer screen for signal transmission and image display. Another assembly choice is to utilize the signal plug to insert into the digital visual interface connecting port instead when the graphics processing card is not installed in the graphics processing card slot.
In general, if a motherboard has different signal input/output devices, a switch integrated circuit is usually installed on the motherboard for path control of signal transmission. The said signal transmission design is commonly seen in the prior art. For example, U.S. Pat. No. 6,874,042 discloses that a switch integrated circuit is utilized for path control of signal transmission between different devices. With reference to claim 1 and FIG. 3 provided by U.S. Pat. No. 6,874,042, a switch integrated circuit installed on a graphics processing card is utilized for path control of signal transmission between the graphics processing card and computer peripheral devices. The aforementioned component configuration may also be applied to a motherboard that simultaneously has a digital display connecting port and a graphics processing card slot. Please refer to FIG. 1, which is a diagram of a motherboard 10 according to the prior art. The motherboard 10 includes a signal control unit 12, a graphics processing card slot 14, a visual interface connecting port 16, and a switch integrated circuit 18. The switch integrated circuit 18 is connected to the signal control unit 12, the graphics processing card slot 14, and the visual interface connecting port 16. If the switch integrated circuit 18 determines that a graphics processing card is installed in the graphics processing card slot 14, the switch integrated circuit 18 transmits image signals received from the signal control unit 12 to the graphics processing card via the graphics processing card slot 14 for further signal processing. On the other hand, if the switch integrated circuit 18 determines that a graphics processing card is not installed in the graphics processing card slot 14, the switch integrated circuit 18 may transmit image signals received from the signal control unit 12 to the visual interface connecting port 16 instead. In such a manner, the motherboard 10 may utilize the switch integrated circuit 18 to achieve the purpose of selective signal output, so as to provide a user with a flexible computer peripheral component assembly.
However, as electronic products increasingly become lighter, thinner, shorter, and smaller, a single output configuration for signals is commonly used in a motherboard recently. That is, a signal output design for a motherboard is changed from a component configuration in which a visual interface connecting port and a graphics processing card slot are simultaneously installed on the motherboard to a component configuration in which only one visual interface connecting port or one graphics processing card slot is installed on the motherboard, so that the manufacturing cost of the motherboard may be reduced. In summary, in single output design for a motherboard, a switch integrated circuit used for selective signal output is unnecessary, since it may increase the manufacturing cost of the motherboard and cause a complicated circuit configuration on the motherboard. However, removal of a switch integrated circuit from a motherboard may also introduce a redesign for the circuit configuration on the motherboard, so that extra manufacturing and research cost may occur.